The present invention relates to a logic circuit, particularly to the art effectively applied to a high speed logic circuit to be formed within a semiconductor integrated circuit, namely to the art effectively applied, for example, to NTL (Non Threshold Logic) or ECL (Emitter Coupled Logic) and moreover to the art effectively applied to the basic logic circuit within a bipolar gate array integrated circuit (for example, refer to Nikkei Electronics, No. 420, P117-120, May 4, 1987, Nikkei Mcgrow-Hill Inc.).
Some NTL and ECL circuits proposed receive low amplitude digital input signal and conduct high speed logic operations. Moreover, has been proposed NTL circuit with output emitter follower and ECL circuit with emitter follower formed by adding the output emitter follower circuit to NTL circuit and ECL circuit (hereinafter, the NTL circuit with output emitter follower is called NTL circuit and the ECL circuit with output emitter follower is called ECL circuit, respectively), high speed logic integrated circuit comprising the basic configuration of NTL circuit and the high speed logic circuit comprising the basic configuration of ECL circuit and NTL circuit.
FIG. 32 is a configuration example of the logic circuit of prior art.
The logic circuit LOG.sub.7 shown in the same figure is formed as an NTL comprising a first transistor Q.sub.36 forming a grounded emitter type phase inversion circuit and a second transistor Q.sub.37 forming an emitter follower output circuit and a negative logic output V.sub.010 can be obtained for an input V.sub.i7 as shown in FIG. 33 by applying an inversion output extracted from the collector of transistor Q.sub.36 to the base of transistor Q.sub.37.
In this case, this logic circuit LOG.sub.7 is provided with a collector load resistance R.sub.34, an emitter bias resistance R.sub.35, a speedup capacitance C.sub.a8 for improving switching operation of transistor Q.sub.36 and an emitter load resistance R36 of transistor Q.sub.37.
The NTL circuit is described, for example, in the Japanese Patent Laid-open No. 63-124615.